Not applicable.
Not applicable.
Glycerol, propane-1,2,3-triol, glycerin (USP), is a trihydric alcohol having a sweet taste, is a clear, water-white viscous, hygroscopic liquid at ordinary room temperatures, which are above its melting point. Glycerin occurs naturally in combined form as glycerides in all animal and vegetable fats and oils, and is recovered as a by-product when these oils are saponified in the process of manufacturing soap, or during the direct splitting of fats in the production of fatty acids. Since 1949 it has also been produced commercially by synthesis from propylene.
The uses of glycerin number in the thousands but the majority of uses relate to the manufacture of synthetic resins and ester gums, drugs, cosmetics, and toothpastes. In the production of alkyd resins, glycerin is employed as a reactive polyol in many formulations. Because of the polyfunctional nature of glycerin, polymer building reactions with difunctional organic acids occur readily. These glycerin based polymers are generally modified further by the addition of monobasic organic acids to achieve resins with either air cure or heat cure properties.
The cosmetic industry has for many years used glycerin in various creams and lotions to keep the skin soft and moist. In addition, glycerin is used in a variety of personal care products such as mouthwash, toothpaste and shampoos where the glycerin serves as a solubilizer and viscosity modifier in the formulation. Glycerin is generally considered to be a flavor enhancer in mouthwash and toothpaste products in contrast to other polyol types which require masking of their particular taste characteristics.
The pharmaceutical industry uses glycerin extensively as a solvent and solubilizer in various drug vehicles for both internal and external uses.
Glycerin is employed as a humectant in tobacco processing. Furthermore, in the food and beverage industry, glycerin is used as a solvent for food flavoring and coloring. Food grade fatty acid esters of glycerin are used extensively in food preparations requiring emulsification.
Glycerin and glycerin derivatives continue to be used extensively in soaps and detergents, hair care products, chewing gum base, lubricants, glass and ceramics and a variety of adhesives.
Glycerin is completely soluble in water and alcohol, slightly soluble in diethyl ether, ethyl acetate and dioxane, and insoluble in hydrocarbons. Glycerin is used to form esters, ethers, halides, amines, aldehydes, and such unsaturated compounds as acrolein. As an alcohol, glycerin also has the ability to form salts such as sodium glyceroxide.
Glycerin derivates include acetals, amines, esters and ethers, the esters being the most widely used. Commercially, the most important are the alkyd resins, which are esters of glycerin and pthalic anhydride.
One of the drawbacks associated with the use of glycerin relates to its susceptibility to color degradation. Glycerin, when exposed to high temperatures such as those associated with the formation of various finished products containing glycerin such as, for example, soap, cosmetics, and the like, has a tendency to thermally degrade, causing colored by-products to form. In many applications associated with the use of glycerin, it is oftentimes desirable for it to remain as color-free as possible.
The present invention is directed to a process for inhibiting thermal degradation of glycerin involving adjusting the pH of glycerin to either: (a) from about 3.5 to about 5 or (b) to above about 10.
Not applicable.